How to Install HardieBacker Cement Board

Written by paul massey| 13/05/2017

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HardieBacker cement board is used as a mould-resistant, non-combustible substrate for floor, wall and countertop stone and ceramic tile installations. For horizontal surfaces such as floors and countertops, HardieBacker cement board is applied over a plywood base or OSB sheathing as a structural base, then attached with a combination of thinset mortar and backerboard screws. For wall applications, the mortar and plywood layers are not required.

Things you need

Tape measure

Carbide-tipped scoring knife or utility knife

Sheetrock square or other straightedge

Thinset mortar mix

3/8-inch notched tile trowel

Power drill with screwdriver bit

Backerboard screws

Webbed fibreglass joint tape

Prepare the subsurface for the HardieBacker cement board installation by inspecting the plywood or OSB to insure that all nail heads or screws are countersunk or flush to the surface. For wall application, make sure the wall-stud surfaces are free of nails, splinters or other imperfections that might interfere with the cement board.

Measure the space for the piece of HardieBacker. For floor or countertop installations, cut the HardieBacker sheet to make certain the joints do not align with the plywood joints beneath. For wall applications, trim the HardieBacker sheet, as required, to split the vertical end joints on the centerline of a wall stud.

Cut the HardieBacker board by first scoring the surface with a carbide-tipped scoring knife, using a sheetrock square or other straightedge as a cutting guide. Apply downward pressure on one side of the cutline and lift upward on the outer edge of the piece to snap the HardieBacker along the scored line.

Mix a quantity of thinset mortar mix following the manufacturer's specification for the area to be covered. For wall applications, mortar is not required beneath the HardieBacker and you can skip the next step.

Apply an even layer of thinset mortar to the floor or countertop plywood surface using a notched tile trowel.

Lay the sheet of HardieBacker cement board onto the thinset mortar or against the wall framing. Secure the sheet in place with backerboard screws spaced approximately 8 inches apart over the field and 2 inches from the edges.

Install all of the HardieBacker sheets.

Cover all of the joints between HardieBacker sheets with webbed fibreglass tape.